Densitometer for measuring the light transmission of a fluid while submerged therein



p 1947- J. E. M ADAMs 2,427,013 DENSITOMETER FOR MEASURING THE LIGHTTRANSMISSION OF A FLUID WHILE SUBMERGED THEREIN Filed Aug. 29, 1944 2Sheets-Shut 1 INVENTOR JESSE EDWARD WADAAE BY m ' ATTORNEY J E. M ADAMSSept. 9, 1941.

DENSITOMETER FOR MEASURING THE LIGHT TRANSMISSION OF A FLUID WHILESUBMERGED THEREIN Filed Aug. 29, 1944 2 Sheets-Sheet 2 Lill. 7 Hnn '2\\\\\&\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\k E Q w 9 V 6R JESSE EDWARD M40446 ATTORNEY Patented Sept. 9, 1947 DENSITOMETER FOR MEASURING THELIGHT TRANSMISSION OF A FLUID WHILE SUBMERGED THEREIN Jesse EdwardMacAdams, Cheverly, Md. Application August 29, 1944, Serial No. 551,763

'2 Claims. (01. 88-14) (Granted under the act of March 3, 1883, as

, Mn amended April 30, 1928; 370 O. G. 757) l This invention relates toinstruments for meas-f urlng the degree of translucency of desired mediawith respect to a selected standard-the standard being variable asdesired and in accordance with the relative translucency of the mediumunder test. Although the instrument is specifically designed formeasurement of light transmission through a liquid or gas in which it issubmerged, it will be recognized that certain principles thereofare.equally applicable to non-submerged use and to the testing of solidspecimens,v smoke detection, etc.

An important object of the present invention is to provide such a deviceincorporating novel means for calibrating the point 'of maximumtransparency, such calibrating means being mechanical in nature and ofsimple and reliable but extremely accurate nature. I

Another object is to provide such a device which is readily portable,which incorporates a sensory portion hermetically sealed and adapted tobe submerged in the material to be tested and electrically connected toa separately encased indicating portion adapted to be located at aremote point or at any desired location to afiord continuous andaccurate indication of ambient translucency without adjustment orcomputation,

Another object is to provide such a densitometer so designed that thecalibration thereof may be quickly and easily changed by the-operator insuch manner that the limits of its indicating range may extend eitherfrom (1) perfect transparency on one extreme to total opacity on theother; or (2) from one to another of certain arbitrary limits chosen forthe requirements of a specific activity, either or both extremes; beingshort of complete transparency or opacity; A related object is tostrument which affords an indication of transparency adapted to beinterpreted in terms of the combined turbidity and light diffusion whichdetermine the distances at which photographs may be made under water.

Referring now to the drawing: I

Fig. 1 is a perspective view of the complete and encased sensorymechanism and the connecting cable assembly by which it is coupled tothe indicator mechanism;

Fig. 2 is a perspective view of the .indicator mechanism;

Fig. 3 is a diagrammatic view of the optical and electrical componentsof theentire system;

.Fig 4 is a longitudinal sectional view of the sensory mechanism takenalong the optical axis;

Fig. 5 is a detail bottom plan view of the lamp socket and itsadjustable supporting means, taken as indicated by the line and arrows5-5 of Fig. 4;

Fig. 6 is a cross sectional view taken substantially on the line 6-6 ofFig. 4 and looking in the direction of the arrows; and

Fig. 7 is a perspective view of the calibrating shutter and adjustingmeans therefor, removed two independent but electrically connectedsecfrom the remainder of the mechanism.

Referring now to the drawing, it will be observed that the completeinstrument comprises tions, viz: the sensory or contro1 housingconprovide such a densitometer which affords full scale deflection ofthe indicating inst'rumentin either of the two cases noted.

A further object is to provide such an instru-..

ment which may b moved about in a large body of liquid; indicating atall times the translucency or fluctuations of translucency attheposition of the sensory element of the instrument. This will berecognized as particularly useful in that stratification and variationsin the thicknesses of strata are common in streams, harbors,settlingbasins and the like. 1

Still another object is to provide such'an intainin the photo-electriccells and light source, and which is adapted to be submerged in thematerial to be tested (this portion of th instrument being illustratedin Figures 1 and 4) and the instrument or indicator housing, shown inFig 2; which althoughelectrically connected to the sensory housing isadapted. to'be placed/at a point where it may be conveniently observedby the operator. As bestshown in Fig. 4, the sensory housing comprises apair of spaced casing sectio'ns 2, 4

I, watertight construction. These are rigidly connected in spaced andaxially aligned relationship by rigid bars 5 shown as of angle section,and

by a tube 6 which also serves as a wire conduit. The main portion ofeach casing section is of substantially cylindrical form, the sectionsbeing mounted coaxially, on the optical axis of the as sembly. Eachsection has a pressure-tight winstrument which may easily be checked andcorrected against a chosen standard, andby means,

of which correct readings may be made by persons relatively unskilledtechnically.

Still another object is to provide such an ining section 2 houses anincandescent lamp I II, a

photo-cell l2, and an interposed heat and light absorbing filter I3. Acollimating lens system I4 is arranged between the lamp l0 and thewindow 8.

On either side of and close to the lamp ID are apertured partitions l5,[6, each having an apersible to locate a diaphragm at the focal point ofthe lens system ll.

The lamp socket l l is movably mounted in such manner as to permituniversal adjustment of the positioning of the bulb, to aid in focusingthe light beam and directing it toward and into the window of theopposite casing section 4. The lamp socket is supported by three equallyspaced screws l1, extending vertically through its base flang Ila andthreaded in an insulating ring 3 removably held in appropriate positionagainst an opening (undesignate'd) in the bottom of casing section 2 byscrews 3A having offset heads and rotatable to release or retain thering and the socket carried thereby. The screw holes in the socket baseflange I la are of such size and shape as to permit the socket to becooked in any direction by unequal adjustment of the screws l1, and thesocket is of course also movable vertically with adjustment of thescrews. Unwanted displacement of the socket with respect to the screwsis prevented by springs l8 on the screws.

Light entering the sensory cell casing section 4 is brought to focus bycondensing lens 24. Also located in this housing is a partition 25having an aperture located at the focal point and barely large enough indiameter to admit the image of the lamp filament, and thereby acting toexclude light transmitted from all other directions than along theoptical axis. The divergent light beam is then directed upon the activesurface of thephotoelectric cell 22, which constitutes the sensory cell.The output and resistance of this cell will be seen to vary with changesof transparency of the substance or material interposed between theWindows 8, 8A. A gate-type shutter 21 is so located between thecondensing lens 24 and diaphragm 25 that the gate, by adjustment, may bemade to cut oil! any desired portion of the light normally reaching thephotoelectric cell 22. Adjustment of the position of the gate iseffected by means of a threaded shaft 28 having a squared end accessiblefrom outside the casing upon removal of a water-tight plug 30. Atraveller nut 29 on the threaded shaft 28 actuates an arm 26 fast uponthe gate shaft, to adjust the gate when shaft 28 is turned.

The density of filter [3 is so selected that light losses therethroughexceed the total losses in all condenser and collimator lenscombinations and I2, 22, which are identical, are accordingly unequalunless a portion of the light trained uponphotocell 22'is cut of! by theshutter 21. Referring to Fig. 3 it will be seen that the photocells areconnected in series. The potential difference between their connectingwires 20 will accordingly be immeasurable when the cells are equallyexcited. As pointed out above, such equal excitation is effected in theinitial adjustment of the apparatus, by adjustment of the gate 21. Ifthe light reaching the photocell 22 is reduced by reason of a reductionof transparency of the medium or object between the windows 8, 8A,however, the resistance of the sensory cell 22 rises proportionately,and a potential difference appears between the connecting wires 20. Suchpotential difference may be measured by a microammeter 32 containedin'the instrument casing and connected to the wires 20 by conductors 2|,which may extend through the cable I illustrated in Figs. 1 and 4. Arelatively high shunt resistance 3| is connected across the' wires 20and the microammeter, the resistance across wires 20 being variablemeans of'the adjustable tap 32. Adjustment of tap 32 varies the responseof the microammeter.- This permits adjustment of the sensitivity of themicroammeter over a wide range, and this meter may in this manner bemade to come to zero either upon a complete blackout of the photocell22, or upon the transmission of any desired amount of light, such asthat passed by an arbitrary standard. A complete blackout of the sensorycell sets up maximum current flow to the indicating instrument and ofcourse maximum deflection. This point is marked zero. Conversely, theposition of the pointer when no current is applied is marked 100%, orany convenient arbitrary marking according to the application of theinstrument. Thus the indication of the instrument increases, logically,with the clarity of the medium under test, although calibration in thereverse manner might of course be used without changing the basicoperation of the system.

Where the device'is to be used in gauging the translucency of liquids,the sensory system assembly illustrated in Figs. 1 and 4, may be supported by the electric cable 9, and simply lowered into the liquid. Thecable is located off center with respect to the assembly so that theunit will hang at an angle, the resultant sloping of the windows 8, 8A,tending to prevent the accumulation of dirt and air bubbles. The unitmay be used in any desired position, however, and upon the opposite endof the assembly a ring as 35 may be provided to permit the unit to beslung in horizontal position as for working close to the bottom wherethis is desired The invention herein describe may be manufactured'andusedby or for the Government of the United States of America forgovernmental purposes without the payment of an royalties thereon ortherefor.

I claim:

1. A densi-tometer comprising a pair of hollow cell housings, eachhaving a fluid-tight window in one wall thereof, a tubular casingconnecting said pair of housings together in spaced relationship withthe windows facing each other, said casing being connected to saidhousings at points substantially laterally spaced from the centrallongitudinal axis there-between, a pair of rigid bars also securing saidhousings together and connected thereto at points on the opposite sideof such longitudinal axis, an optical system comprising a pair of lightsensitive cells, one cell being located in each of said cell housings, asource of light located in one of said cell housings along with one ofsaid cells, but spaced therefrom and located intermediate said cells anddisposed upon the focal point of said condensing lens, said partitionhaving an aperture on said optical axis of the cross-sectional area ofthe focused beam at said focal point, a shutter adjaoent'said partitionpositioned to intercept a part of the light beam, said shutter beingmounted for pivotal adjustment to vary the size of the intercepted partof the beam and means adjacent the source of light .and within the cellhousingcontaining said collivmating lens for preventing lighttransmitted through said collimating lens from sources substantiallyspaced from the said optical axis from reaching the cell in saidhousing.

2. As a unitary article, a densitometer comprising a pair of hollow cellhousings, each having a fluid-tight window in one wall thereof, atubular casing connecting said pair of housings together in spacedrelationship with the windows facing each other, said casing beingconnected to said housings at points substantially laterally spaced fromthe central longitudinal axis therebetween, a pair of rigid bars alsosecuring said housings together and connected thereto at points on theopposite side of such longitudinal axis, an optical system comprising apair of light sensitive cells, one cell' being located in each of saidcell housings, a source of light located in one of said cell housingsalong with one of said cells, but spaced therefrom and locatedintermediate said cells and disposed upon an optical axis between saidcells, said optical axis extending intermediate said tubular casing andsaid rigid bars; means for indicatingdifierences in the amounts of lightreaching saidcells comprising a, separate housing, an electricalindicator means in said separate housing, a cable connecting saidindicator housing to one of said cell housings at a point laterallyspaced from said optical axis, a comparison circuit comprising wiresextending from said electrical indicator means through said cable intoone of said housings, some of said wires besaid other cell housingintermediate the cell and v \said condensing lens ancblocated atsubstantially .of dimensions not substantially greater than those ingconnected to the cell in said housing. the other wires extending throughsaid tubular casing to said other cell in said other housing; a'

lens system positioned in said one cell housing on said optical axis andintermediate said source of light and the housing Window for projectinga collimated beam of light from said source of light through the spacebetween said cell housings, said lens system comprising a collimatinglens spaced from the light source a, distance substantially equal to thefocal length of said lens, a

condensing lens positionedon said optical axisin 1 the other cellhousing,"said condensing'lensfbe ing spaced from the cellins'aid otherhousingdistance substantially exceeding a light intercepting par 'iohousingintermediate the lens and located at subst of said condensinglensg'said aperture on said optical an substantially greater thedimensions not se' ,of' the crosssectional area of the focusedbeam atsaid focal point, a shutter adjacent said'partition positioned tointercept a part of the light beam, said shutter being mounted forpivotal adjustment to vary the size of the intercepted part of the beamand means adjacent the source of, light and within the cell housingcontaining said collimating lens for preventing light transmittedthrough said collimating lens from sources substantially spaced from thesaid optical axis from reaching the cell in said housing.

JESSE EDWARD MACADAMS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS OTHER REFERENCES Radio News for June, 1944; pagecited.

(Copy in Scientific Library, U. S. Patent Ofiice.)

